1. Technical Field
The present invention relates to a color filter manufacturing method, a color filter, an image display device, and an electronic device.
2. Related Art
Color filters are generally used in liquid crystal display devices (LCD) and the like that display color.
Color filters have conventionally been manufactured using a so-called photolithography method in which a coating film composed of a material (color layer formation composition) that includes a colorant, a photosensitive resin, a functional monomer, a polymerization initiator, and other components is formed on a substrate, and then photosensitive processing for radiating light via a photomask, development processing, and the like are performed. In such a method, the color filters are usually manufactured by repeating a process in which a coating film corresponding to each color is formed on substantially the entire surface of the substrate, only a portion of the coating film is cured, and most of the film other than the cured portion is removed, so that there is no color overlap. Therefore, only a portion of the coating film formed in color filter manufacturing remains as a color layer in the finished color filter, and most of the coating film is removed in the manufacturing process. Therefore, not only does the manufacturing cost of the color filter increase, but the process is also undesirable from the perspective of resource saving.
Methods have recently been proposed for forming the color layer of a color filter by using an inkjet head (droplet discharge head) to discharge a material (color layer formation ink; hereinafter referred to as ink) for forming a color layer in a plurality of cells provided on a substrate (see Japanese Laid-Open Patent Application No. 2002-372613, for example). In such a method, because the discharge position and the like of the ink droplets are easily controlled, and waste of the color layer formation composition can be reduced, the environmental impact can be reduced, and manufacturing cost can also be minimized.
The ink used to manufacture the color filter includes a colorant, a resin material, and other components. Therefore, such an ink usually has a high viscosity. In manufacturing the color filter, the ink is usually discharged while the substrate is moved relative to the inkjet head for the sake of productivity.
When an ink having such a relatively high viscosity is discharged, trailing can sometimes occur. Depending on the landing position of the ink, the trail portion (hereinafter referred to as the satellite) is recovered within the same cell when the trailing breaks off, but the satellite sometimes enters an adjacent cell in conjunction with the relative movement of the substrate, and the problem of mixing between adjacent cells thereby occurs. As a result, a color layer having the desired coloration cannot be formed, and the color reproduction properties of the manufactured color filter are adversely affected. The cell height and shape may be designed so as to prevent such mixing, but when the height of the cells is increased, a large amount of ink must be discharged, the thickness of the color layer increases, and the productivity and light usage efficiency are reduced. The problem of color mixing such as described above is severe when the frequency of discharge from the inkjet head is increased, and the speed of relative movement of the substrate is increased in order to enhance productivity.